It should be much faster if you install on the SSD, and an unnoticeable ittle bit faster if you install it on the HDD.
I upgraded my PC with a kingston hyperx 3k ssd 120gb and I am using it as a boot drive.
It works fine, but now if I try to install a program onto the SSD or HDD the instillation can take over a hour. Even for old games like Simscity 3000.
Motherboard: ASRock A75M-HVD
PSU: 600Watt ACE ATX
Graphics: AMD Readon HD 5500
SSD: Kingston Hyperx 3k 120GB
HDD: 500GB (not sure of the make but I can find out if needed)
External HDD: Seagate GoFlex 1TB
Also have a DVD and a Blu-ray drive
Any help is appreciated